Bug 852847 - Part 1: Disable browserElement_oop_KeyEvents.html. r=kk1ff

In fact this test was already disabled; the OOP version was the same as
the in-process version because the test explicitly disabled OOP tabs.

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extra : rebase_source : 7bcfb88e7368f72d1df863c0c026c7b0549caa77
Bug 852847 - Part 2: Do things later in our browser-element tests, thus avoiding doing things before the browser-element machinery has loaded. r=kk1ff

Also set network.disable.ipc.security to true and leave it that way. This prevents security errors in the tests which happen when we pop the pref.

--HG--
extra : rebase_source : 95f7ca7c3b71cdc0e3e6fd1cfb663a5653f3ab6f
Bug 852847 - Part 3: Re-enable some browser-element tests. r=kk1ff

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extra : rebase_source : be2c103555342f53eb8e5550058daed73153f47f